It is known to provide an indicator on a hose for a hand shower to indicate the temperature of the water in the device. For instance commonly owned U.S. Pat. No. 5,160,197 Klose describes a hand shower having an upstream end connected to a downstream end of a hose to receive water therefrom by a fitting having a snap coupling and a display. The snap coupling has a male part fixed on one of the ends, a female part fixed on the other of the ends and fittable over the male part, and a latch in the female part for releasably retaining the male part therein. The display is mounted on one of the parts and gives a readout of the temperature of the water flowing through the coupling.
U.S. Pat. No. 3,960,016 of P. Symmons describes a temperature indicator that is mounted in the escutcheon of a recessed mixing valve. This device is wholly mechanical, with a standard bimetallic helix positioned in the flow of mixed water and attached to a rod on which is carried a pointer that is visible adjacent a scale through a window on the escutcheon.
German patent document 3,330,585 filed 25 August 1983 by W. Brunnenkant describes another such arrangement having a housing that is fitted between the mixing valve and the upstream end of the faucet. A sensor in the housing is in heat-conducting relationship with water passing through it and is connected to the input of a battery-powered circuit whose output drives a digital display to show the water temperature.
Such systems are typically very good in their individual applications, but cannot be adapted to different uses. Thus a retrofit temperature indicator that is to be mounted on a faucet or hose is completely different from one that is incorporated in a below-deck or recessed fitting.